Trouble with back-references on Windows

randy1234 has asked for the wisdom of the Perl Monks concerning the following question:

I'm having trouble using back-references in a Windows one-liner and hoping someone knows what I'm doing wrong.

I can use a single back-reference but as soon as I try more than one it breaks.

Environment:

Powershell on Windows 10 (because it's seemingly more sane than trying to use the standard Command prompt).
Strawberry Perl (v5.26.0))

> echo "abcd" | perl -nle '/(b).(d)/ && print "$1" '
b
> echo "abcd" | perl -nle '/(b).(d)/ && print "$2" '
d
> echo "abcd" | perl -nle '/(b).(d)/ && print "$1 $2" '
Can't open $2 : No such file or directory.
[download]

The error changed when I tried to escape the double-quotes with a backslash and a back-tick:

> echo "abcd" | perl -nle '/(b).(d)/ && print \`"$1 $2\`" '
Can't find string terminator "`" anywhere before EOF at -e line 1.
[download]

Any ideas?

Comment on Trouble with back-references on Windows Select or Download Code

Replies are listed 'Best First'.
Re: Trouble with back-references on Windows by poj (Abbot) on Mar 14, 2019 at 19:01 UTC
Any ideas? echo "abcd" \| perl -nle '/(b).(d)/ && print \"$1 $2\"' poj	[reply]
Re^2: Trouble with back-references on Windows by randy1234 (Initiate) on Mar 14, 2019 at 19:30 UTC
Thanks poj! I was using quotes for a more complicated regex earlier in the day (without the back-references) and found that it only worked with BOTH the backslash and the back-tick so I neglected to try it it in this instance.	[reply]
Re: Trouble with back-references on Windows by Laurent_R (Canon) on Mar 14, 2019 at 23:23 UTC
Quoting is somewhat of a mess in Perl one-liners under Windows (which is one of the reasons why I prefer to use Cygwin or `bash` for Windows when I have to work with Windows). It is usually better to use double quotes for the one-liner script, but that makes interpolating quotes slightly more difficult to use. This works with the Windows command prompt: `C:\Users\Laurent>echo "abcd" \| perl -nle "/(b).(d)/ && print qq/$1 $2/ +;" b d` [download]	[reply] [d/l] [select]