Re^4: Windows and backslashes and replacements oh my!

in reply to Re^3: Windows and backslashes and replacements oh my!
in thread Windows and backslashes and replacements oh my!

One $bs is sufficient in my tests:

d:\>perl -E"for $x (qw/C:\berrybrew\test C:\berrybrew /) {$_=$x; $bs=c
+hr(92); s/berrybrew(?!\\+test)/berrybrew${bs}test/; say}"
C:\berrybrew\test
C:\berrybrew\test

d:\>
[download]

> Obviously Perl needs to escape the backslash inside a regex

not after interpolation of variables like $bs

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

Comment on Re^4: Windows and backslashes and replacements oh my! Download Code

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Re^5: Windows and backslashes and replacements oh my! (two escapings in LHS of s///) by LanX (Saint) on Jun 19, 2021 at 12:09 UTC
> > Obviously Perl needs to escape the backslash inside a regex > not after interpolation of variables like $bs I have to correct myself, it depends on the side of the substitution the right side is a simple doublequoted string, so after interpolation no escaping but the left side is a regex with two levels of escaping string interpolation with escaping first, i.e. `\$bs` won't be interpolated regex interpretation with escaping first, i.e. `/\/` is not a quantifier but literal `` same with `/$bs*/` compare `d:\>perl -E"for $x (qw/C:\berrybrew\test C:\berrybrew /) {$_=$x; $bs=c +hr(92); s#$bs$bs#<${bs}>#g; say}" C:<\>berrybrew<\>test C:<\>berrybrew d:\>` [download] or to eliminate the Win command line `use v5.12; use warnings; use Data::Dump; my $bs=chr(92); for my $x (qw/C:\berrybrew\test C:\berrybrew /) { $_=$x; s#$bs$bs#<${bs}>#g; say; #ddx $_; } $_='$bs'; s/\$bs/<$&>/; say;` [download] `C:<\>berrybrew<\>test C:<\>berrybrew <$bs>` [download] so this might be the OPs original problem see also s/RegEx/substitutions/: Variable interpolation and when to use /e - modifiers Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]

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Re^5: Windows and backslashes and replacements oh my! (two escapings in LHS of s///)
by LanX (Saint) on Jun 19, 2021 at 12:09 UTC

> > Obviously Perl needs to escape the backslash inside a regex

> not after interpolation of variables like $bs

I have to correct myself, it depends on the side of the substitution

the right side is a simple doublequoted string, so after interpolation no escaping
but the left side is a regex with two levels of escaping
1. string interpolation with escaping first, i.e. \$bs won't be interpolated
2. regex interpretation with escaping first, i.e. /\*/ is not a quantifier but literal * same with /$bs*/

d:\>perl -E"for $x (qw/C:\berrybrew\test C:\berrybrew /) {$_=$x; $bs=c
+hr(92); s#$bs$bs#<${bs}>#g; say}"
C:<\>berrybrew<\>test
C:<\>berrybrew

d:\>
[download]

or to eliminate the Win command line

use v5.12;
use warnings;
use Data::Dump;

my $bs=chr(92);

for my $x (qw/C:\berrybrew\test C:\berrybrew /) {
    $_=$x;
    s#$bs$bs#<${bs}>#g;
    say;
    #ddx $_;
}

$_='$bs';
s/\$bs/<$&>/;
say;
[download]

C:<\>berrybrew<\>test
C:<\>berrybrew
<$bs>
[download]