Extracting regex from string

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

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Re: Extracting regex from string by AnomalousMonk (Archbishop) on Feb 18, 2017 at 05:56 UTC
Please see Re: Evaluating $1 construct in literal replacement expression to begin your journey. Update: Or am I reading more into your question than you intend? Maybe just: `c:\@Work\Perl\monks>perl -wMstrict -le "my $string = 'hello $1'; ;; if ('good morning all' =~ /good morning (\w+)/) { my $evaled_string = eval qq{ qq{$string} }; print qq{>$evaled_string<}; } " >hello all<` [download] See eval. ("After parsing a file and extracting the following line..." Note that using string `eval` in this way is a potentially dangerous operation.) Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: Extracting regex from string by LanX (Saint) on Feb 18, 2017 at 10:28 UTC
Please edit your post to correct code-tags. Additionally `'hello world add'` doesn't make sense. Please see How do I post a question effectively? The better the question the better the answers! I need to guess what you really want: `my $input = "good morning all"; my $pattern = qr/good morning (\w+)/; my $replace = '"hello $1"'; my $output = $input =~ s/$pattern/$replace/ree; print $output;` [download] `hello all` [download] Please be sure to have full control of the $replace strings since the eval /ee would lead to security issues. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply] [d/l] [select]
Re: Extracting regex from string by LanX (Saint) on Feb 18, 2017 at 12:33 UTC
as an alternative which avoids the risks of eval try `sprintf` `$repl = 'hallo %s'; $string = sprintf $repl,$1,$2,$3,$4,$5,$6,$7,$8,$9;` [download] Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply] [d/l]
Re^2: Extracting regex from string by AnomalousMonk (Archbishop) on Feb 19, 2017 at 20:17 UTC
Also, the n`$` "format parameter index" attribute of the sprintf format specifier can free you from the capture variable lockstep of $1 .. $ n: `c:\@Work\Perl\monks>perl -wMstrict -le "my $template = 'all the %3$s %1$s %2$s'; my $extract = 'all at sea in ships'; ;; if ($extract =~ m{ \A all \s+ (\w+) \s+ (\w+) \s+ in \s+ (\w+) \z }xm +s) { my $string = sprintf $template, $1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13; print qq{>$string<}; } " >all the ships at sea<` [download] Both safe and flexible. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: Extracting regex from string by BillKSmith (Monsignor) on Feb 18, 2017 at 19:29 UTC
In your example, $1 seems to take the value 'world'. Where did that come from? It is not in either of your input strings. When is it interpolated? Please post a complete example with both the actual and the desired output. Bill	[reply]