Should I fear eval? (want to do two things on the left side of an if/unless)

tphyahoo has asked for the wisdom of the Perl Monks concerning the following question:

I cooked up the following one liner

$ perl -e 'my $type="blee"; eval { print "bad type\n"; print "blee\n" 
+} unless ($type eq "newer" || $type eq "older")'
bad type
blee
[download]

It has an eval in it, because I want to "do two semicolon-separated things" on the left side of an if/unless. What I mean is, if this bit in curly brackets was on the right side of the if/unless, I wouldn't need the eval statement, it would just flow from the syntax.

I never ever use eval, here I just kind of popped it out to see what would happen.

So I guess what I'm asking is, other than having that extra "eval" statement, is there something else wrong with what I am doing here?

Should I fear eval?

And should I fear trying to do more than one "semicolon-separated thing" on the left side of an if/unless statement?

UPDATE:

1) Changed single quotes to double quotes.

2) Obviously, I wanted "do" here. Thanks for helping -- I think I got three answers to my question in under 45 seconds, and not a single RTFM. wow :)

Comment on Should I fear eval? (want to do two things on the left side of an if/unless) Download Code

Replies are listed 'Best First'.
Re: Should I fear eval? (want to do two things on the left side of an if/unless) by Corion (Patriarch) on Aug 10, 2006 at 12:17 UTC
And should I fear trying to do more than one "semicolon-separated thing" on the left side of an if/unless statement? Yes `:-)`. I'd use `do{...}` over `eval{...}` because `do` doesn't have the nasty habit of eating fatal errors unless I explicitly check for them. I'd still reverse the logic and put the consequent to the right side: `perl -e 'my $type="blee"; if ($type ne "newer" and $type ne "older") { + print "bad type\n"; print "blee\n"}'` [download]	[reply] [d/l] [select]
Re: Should I fear eval? (want to do two things on the left side of an if/unless) by davorg (Chancellor) on Aug 10, 2006 at 12:20 UTC
Why not just use the more traditional "if/unless" construct? `unless ($type eq 'newer' \|\| $type eq 'older') { print "bad type\n"; print "blee\n"; }` [download] Alternatively, you could use "do": `do { print "bad type\n"; print "blee\n"; } unless ($type eq 'newer' \|\| $type eq 'older');` [download] "eval" is completely inappropriate in this instance. You shouldn't fear using "eval" - just abusing it :-: -- <http://dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply] [d/l] [select]
Re: Should I fear eval? (want to do two things on the left side of an if/unless) by jhourcle (Prior) on Aug 10, 2006 at 12:20 UTC
If you just want to do two things, you can use 'do' in place of 'eval'. Also, watch your quotes inside a one liner (you're using single quotes inside single quotes)	[reply]
Re: Should I fear eval? (want to do two things on the left side of an if/unless) by ikegami (Patriarch) on Aug 10, 2006 at 15:09 UTC
Should you fear `eval`? It depends on which `eval`.	[reply] [d/l] [select]
Re^2: Should I fear eval? (want to do two things on the left side of an if/unless) by Anonymous Monk on Aug 11, 2006 at 08:30 UTC
If you're wondering if you should fear eval, the answer is yes, as you don't know eval.	[reply]
Re: Should I fear eval? (want to do two things on the left side of an if/unless) by broquaint (Abbot) on Aug 11, 2006 at 11:20 UTC
If you're not using compound statements you can just put the comma operator to use e.g `my $type="blee"; print("bad type\n"), print("blee\n") unless ($type eq "newer" \|\| $type eq "older");` [download] HTH `_________ broquaint`	[reply] [d/l]


Come for the quick hacks, stay for the epiphanies.
	PerlMonks