case escape characters

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

Good day, monks.. I'm working on a small parser and in this script I require a function that would be able to return a special 'escape' (excuse me for poor jargon) character (such as'\U' etc) based on the case of a string passed to the sub as the first parameter. So, if my string is in uppercase, the subroutine should return '\U', it should return '\L' otherwise. For example,

my $esc_char = get_escape_case("S");
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would return '\U' escape character. I may then use it (or so I hope to) to format any other string (either uppercase or lowercase it) by simply prepending the escape character in an expression like this:

my $case_formatted_string = $esc_char ."FoobAr";
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In this example (where $esc_char is '\U') $case_formatted_string should become 'FOOBAR' (since "S" is in uppercase).

The only problem that I'm facing now is how do I actually apply this escape character to a string? I've tried one obvious way in a sample code below but it didn't work:

use strict;

# determine case of a character
# and return appropriate 'control' code.
sub get_escape_case
{
    my ($char) = @_;
    if ($char eq "\U$char") {
       return '\U'; 
    } else {
       return '\L';
    }
}

# this wouldn't work...
print get_escape_case("S")."stuff\n";

# while this works..
print "\Ustuff\n";
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I guess I might have to use a special 'code' for the escape character? Could anyone lead me in the right path? Thank you. ;-)

"There is no system but GNU, and Linux is one of its kernels." -- Confession of Faith

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Re: case escape characters
by I0 (Priest) on Mar 02, 2002 at 05:13 UTC

print &{sub{local($c,$_)=@_;$c x=length;$c^lc$c^lc}}("S","stuff");

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(jeffa) 2Re: case escape characters

by jeffa (Bishop) on Mar 02, 2002 at 13:51 UTC

x=length

$c^lc$c^lc

my $c = 'a';
my $d = 'A';
$_ = 'stuff';

print $c^lc$c^lc;
print $d^lc$d^lc;
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jeffa most humbly bows

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Re: case escape characters
by synapse0 (Pilgrim) on Mar 02, 2002 at 03:40 UTC

$string = adjust_case('s', "stuff\n");
print $string; # which would print Stuff with a newline
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Sleep Deprived

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Re: Re: case escape characters

by vladb (Vicar) on Mar 02, 2002 at 04:18 UTC

use strict;

sub to_case
{
    my ($char) = @_;

    if ($char eq "\U$char") {
        return sub {uc(shift)};
    } else {
        return sub {lc(shift)};
    }
}

print to_case("FOO")->("bAr") ."\n";
print to_case("foo")->("BaR") ."\n";
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BAR
bar
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"There is no system but GNU, and Linux is one of its kernels." -- Confession of Faith

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