Interpolating $1 within a variable

s0ttle has asked for the wisdom of the Perl Monks concerning the following question:

Monks,
This works as expected:

perl -le '$_=q(ab cdefg);s/(^\w+)/$1,/;print;'
[download]

but I cannot seem to find a way to get this to work:

perl -le '$_=q(ab cdefg);$x=q($1,);s/(^\w+)/$x/;print;'
[download]

I thought about using eval:

perl -le '$_=q(ab cdefg);$x=q($1,);s/(^\w+)/eval$x/e;print;'
[download]

but that did not do what I needed which is an output of: ab, cdefg
I tried using qq("") with /ee:

perl -le '$_=q(ab cdefg);$x=q($1,);s/(^\w+)/qq("$x")/ee;print;'
[download]

it worked!, but unfortunately puts "" around regular strings. Any suggestions on how I can interpolate $1 inside of a variable with out any side effects similar to qq("")? -tengo mas que aprender

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Re: Interpolating $1 within a variable by tachyon (Chancellor) on Oct 27, 2001 at 17:20 UTC
Oops I missed the fact that you lose the comma doing that - yellow is not the best highlight color BTW. This preserves the comma for you: `$_=q(ab cdefg); $x=q($1,); s#(^\w+)# my $sub = $1; $x=~s/\$1/$sub/; $x #e; print;` [download] Update That will permanently change the value in $x which you probably don't want so I should have used a scoped temp var like this: `s#(^\w+)# my $sub = $1; (my $subx = $x) =~ s/\$1/$sub/; $subx #e;` [download] cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply] [d/l] [select]
Re: Interpolating $1 within a variable by Zaxo (Archbishop) on Oct 27, 2001 at 18:08 UTC
This method may not suit you, since it does not capture the initial string, but it evades the string evaluation technicalities: `$ perl -le '$_=q(ab cdefg);s/(?<=\w)\b/,/;print;'` [download] This inserts a comma at the first word-nonword boundary in the string After Compline, Zaxo	[reply] [d/l]
Re: Interpolating $1 within a variable by tachyon (Chancellor) on Oct 27, 2001 at 17:11 UTC
You need the /ee modifier. The first /e changes $x to $1, and the next interpolates in the value in $1. You do not need to go qq("$x"). qq/foo/ is the same as "foo" so you effectively have "\"foo\"" You only need to go $x vis `$_=q(ab cdefg); $x=q($1,); s/(^\w+)/$x/ee; print;` [download] cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply] [d/l]
Re: Interpolating $1 within a variable by s0ttle (Scribe) on Oct 27, 2001 at 17:22 UTC
Yes, I realized all of that, but I still don't get the comma in the output. :\	[reply]
Re: Interpolating $1 within a variable by chromatic (Archbishop) on Oct 28, 2001 at 02:16 UTC
For almost every class of problem where this is a possible answer, it is the wrong answer. Zaxo's suggestion is the best so far. Perhaps if you were to describe your intent, we would be able to give you a better kind of solution. (By wrong, I mean "fragile", "prone to unforseen flaws", and "swatting flies with a sledgehammer".)	[reply]
Re: Interpolating $1 within a variable by CharlesClarkson (Curate) on Oct 28, 2001 at 11:21 UTC
Er, I'm confused: `$_ = q(ab cdefg); $x = q($1,); s/(^\w+)/qq("$x")/ee; print;` [download] produced: ab, cdefg What do you mean by: it worked!, but unfortunately puts "" around regular strings. Any suggestions on how I can interpolate $1 inside of a variable with out any side effects similar to qq("")? What side effects? Charles K. Clarkson	[reply] [d/l]
Re: Interpolating $1 within a variable by s0ttle (Scribe) on Oct 29, 2001 at 14:43 UTC
What I meant was that when $x=q(ab,); the output was: "ab," cdefg but I found out why it was doing this. I had forgotten to add the extra /e and so I kept running: `perl -le '$_=q(ab cdefg);$x=q(ab,);s/(^\w+)/qq("$x")/e;print;'` [download] But the problem is fixed now. Thank you monks. -tengo mas que aprender	[reply] [d/l]

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