Re: Regex - Is there any way to control when the contents of a variable are interpolated? (Using "$1" and '$1' in regex replacements)

Several problems here:

Array indexing starts at 0, not 1.
In character classes (inside square brackets in a regex) you do not have to backslash brackets. ^ on the non-first position in a character class stands for itself.
There are no capturing parentheses in the code, so $1 would be empty even if it worked.
You have to evaluate the right hand side to turn the string $1 into the variable.

#!/usr/bin/perl
use warnings;
use strict;

sub replace {
    s/$_[0]/$_[1]/eeg;
}


$_ = 'a { b } c ( d ) e';

my $nobrackets = qr/[^{}]+/;
replace(qr/\{($nobrackets)\}/, '$1');

print "$_\n";
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Re^2: Regex - Is there any way to control when the contents of a variable are interpolated? (Using "$1" and '$1' in regex replacements) by JDoolin (Novice) on Mar 14, 2014 at 17:12 UTC
Hello, thank you for your prompt response. It appears that s///eeg gives me part of what I want. It seems to interpolate the $1 when it is alone. But it is an incomplete solution for me. If instead of just getting rid of the brackets I want to replace them with words: `#!/usr/bin/perl use warnings; use strict; sub replace { s/$_[0]/$_[1]/eeg; } $_ = 'a { b } c ( d ) e'; my $nobrackets = qr/[^\{^\}]+/; replace(qr/\{($nobrackets)\}/, ' leftbracket $1 rightbracket '); # I w +ant to replace the brackets with the words leftbracket and rightbrack +et. print "$_\n";` [download] This appears to make the { b } vanish entirely.	[reply] [d/l]
Re^3: Regex - Is there any way to control when the contents of a variable are interpolated? (Using "$1" and '$1' in regex replacements) by AnomalousMonk (Archbishop) on Mar 15, 2014 at 00:41 UTC
`my $nobrackets = qr/[^\{^\}]+/;` A peripheral problem, but please take another look at choroba's second point above. Please see Character Classes and other Special Escapes in perlre, also discussions of character classes in Using character classes in perlrequick, and more extensively Using character classes in perlretut.	[reply] [d/l]
Re^4: Regex - Is there any way to control when the contents of a variable are interpolated? (Using "$1" and '$1' in regex replacements) by JDoolin (Novice) on Mar 15, 2014 at 18:58 UTC
Yes, I misunderstood his comment above. "2. In character classes (inside square brackets in a regex) you do not have to backslash brackets. ^ on the non-first position in a character class stands for itself." When I read 'you do not have to...' I understood that the backslashes are optional, but decided I liked to use them anyway. I completely missed his more important point here, that the repeated ^ actually negates the ^ character.	[reply]