Re^2: doing tr/// on-the-fly?

Thanks. That helps some.

Changing the code to the following:

#!/usr/bin/env perl

use strict;

my $s = 'eabcde';
my $t = $s;

print "$t\n";
$t =~ tr/abcd/efgh/;
print "$t\n";

print '*' x 4, $/;

my $search = 'abcd';
my $replace = 'efgh';

$t = $s;
print "$t\n";

eval {
   $t =~ tr/$search/$replace/;
};

print "$search\n";
print "$replace\n";
print "$t\n";
[download]

Gives me the results:

eabcde
eefghe
****
eabcde
abcd
efgh
epbade
[download]

I don't see why the results of tr/// differ.

Comment on Re^2: doing tr/// on-the-fly? Select or Download Code

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Re^3: doing tr/// on-the-fly? by ikegami (Patriarch) on Mar 18, 2010 at 04:27 UTC
`eval BLOCK` and `eval EXPR`, despite the similarity in name, are very different functions. You might know the former as `try`, an exception catching block. The latter also catches exceptions, but its goal is to parse and run dynamically generated Perl code.	[reply] [d/l] [select]
Re^3: doing tr/// on-the-fly? by Anonymous Monk on Mar 18, 2010 at 01:31 UTC
Okay, I didn't duplicate exactly what you said. The following code: `#!/usr/bin/env perl use strict; my $s = 'eabcde'; my $t = $s; print "$t\n"; $t =~ tr/abcd/efgh/; print "$t\n"; print '' x 4, $/; my $search = 'abcd'; my $replace = 'efgh'; $t = $s; print "$t\n"; eval "\$t =~ tr/$search/$replace/"; print "$search\n"; print "$replace\n"; print "$t\n";` [download] ...does give me the expected results: `eabcde eefghe *** eabcde abcd efgh eefghe` [download] Why the difference?	[reply] [d/l] [select]
Re^4: doing tr/// on-the-fly? by jwkrahn (Abbot) on Mar 18, 2010 at 01:43 UTC
Because: `eval { $t =~ tr/$search/$replace/; };` [download] is just normal perl code where there is no interpolation so '$' is replaced with '$' and 's' is replaced with 'r' and 'e' is replaced with 'e' and 'a' is replaced with 'p', etc. while using string eval interpolates the variables $search and $replace.	[reply] [d/l]