sub definedWord
{
    my( $word )= @_;
    return eval "use strict; my \$x= sub { $word  }; 1"
        ||  ( warn("$@\n"), $@ !~ /^Bareword/ );
}

@ARGV= qw( definedWord time system foo BEGIN if -e lt goto last )
    if  ! @ARGV;
for(  @ARGV   ) {
    printf "$_:\t%sdefined\n", definedWord($_) ? "" : "UN";
}
[download]

is one interesting interpretation, producing:

definedWord:    defined
time:   defined
system: defined
Bareword "foo" not allowed while "strict subs" in use at (eval 4) line
+ 1.

foo:    UNdefined
BEGIN:  defined
syntax error at (eval 6) line 1, at EOF

if:     defined
-e:     defined
syntax error at (eval 8) line 1, near "{ lt"

lt:     defined
goto:   defined
last:   defined
[download]

Neat! It seems to consider a lot of things to be defined that aren't so executable. All of these, for instance:

@ARGV= qw( ; "foo" 123 {} [] ) if ! @ARGV;
# etc.
__END__
;:      defined
"foo":  defined
123:    defined
{}:     defined
[]:     defined
[download]

As the name implies, it is meant to be passed a word. (Since non-words can't be called as subroutines without unusual syntax.)

- tye        

If that really matters for an example, definedWord could be just powered with regex. ++tye.

---

Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!

I like this idea a lot. Thanks for the suggestion.

my $is_function = $package->can($function_name);
[download]

This also does not work with built-ins:

use List::Util qw(min);
sub foo {}
$x = time();
foreach my $thing ( qw( x foo min time ) ) {
    printf "$thing is code: %s\n",
        ( ref *{$main::{$thing}}{CODE} ) ? 'Yes' : 'No';
}
__END__
x is code: No
foo is code: Yes
min is code: Yes
time is code: No
[download]

Perhaps you could tell us what problem you're really trying to solve?

If you have some string, and you want to know if it could do something under eval without actually executing it, perhaps you could use 'perl -c' for that. Or, to be really ugly, shell out and see what 'perldoc -f' has to say about it (being very careful about quoting the argument, of course). That would detect built-ins, and you could use one of the other methods listed here for detecting everything else.

I'm trying to examine a string of input and decide which words m/\b(\w+)\b/g are executable, without executing them. If executable I leave them alone; if not I do something off-topic with them.

Just call it and see what happens.

sub bar { print 'woot' }

for my $thing (qw/ foo bar /){
    print "$thing :$/";
    eval{
      no strict refs;
      &{$thing}(@_);  # possibly a nasty symbolic reference
    };
    warn "You can not call $thing: $@ " if $@;
}
[download]

gives you something like:

The main point being, that you can just catch the die from eval and move on.

Why ask if something looks like it will fail, when you can just suck it and see?

if you're involving objects, UNIVERSAL's can may also interest you

I'm trying to do the opposite of what you're suggesting. I explicitly don't want to call it if it's a function.

$func = "format_hard_drive";
print "Good news, function exists!" if eval { &$func() };
[download]

You can do it one of two ways.

1. Check that the thing is valid before hand (as ref $coderef in my class below does)
2. Check when you call that the result is valid (as the trigger_event sub will do if you remove the test in the first point)

At the risk of getting a TL;DR, here's something that takes coderefs and then dispatches events with them, as I wrote this, I realised that it's surprisingly long for a simple example ;)

This is the class that takes care of dispatching the events (to a single handler for each event type)

Read more... (2 kB)

This is the client code, that registeres event handlers (to be used as callbacks) and triggers the actual events on the object. Normally, the object would find it's own events, and handle them within a run() type method (Tl's MainLoop for example)

Read more... (2 kB)
Read more... (1221 Bytes)

The class will reject 'antelope' because it's not a real coderef, although if you were to pass in 'main::antelope' as the name, and remove the check for ref $coderef, you should be able to use just names of subs. I don't see why you would want to do this, since it's the same number of characters to write \& as it is to enclose the sub's name quote likes

Justification: this does answer your question about checking if it's callable before hand (because it uses ref $subref to decide if it can be callled (long before the events actually turn up). This is a fairly painless way to check if something is callable, you can also use anonymous subs if you want

Hope this helps.

@_=qw; ask f00li5h to appear and remain for a moment of pretend better than a lifetime;;s;;@_[map hex,split'',B204316D8C2A4516DE];;y/05/os/&print;