What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string?

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

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Re: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? (smor) by tye (Sage) on Mar 15, 2012 at 19:59 UTC
`s/\$ENV{(\w+)}/$ENV{$1}/ge;` [download] That doesn't solve the 'problem' of wanting to have a literal '`$ENV{X}`' kept unchanged for some reason. That seems unlikely enough of a desire that I'm not sure I'd even do anything about it. Though I might prevent substitution if no such environment var is set: `s/\$ENV{(\w+)}/ exists $ENV{$1} ? $ENV{$1} : "\$ENV{$1}" /ge;` [download] - tye	[reply] [d/l] [select]
Re^2: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? (smor) by emilbarton (Scribe) on Mar 15, 2012 at 20:25 UTC
Nice!	[reply]
Re: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? by jeffa (Bishop) on Mar 15, 2012 at 19:58 UTC
I would simply store the relative "path" part and leave the `$ENV{HOME}/` out completely. Then, after you parse the XML file you can prepend the value of $ENV{HOME}, perhaps with a rule that only if the value is relative and not absolute. jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]
Re^2: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? by emilbarton (Scribe) on Mar 15, 2012 at 20:28 UTC
Yes I wanted the user to be able to change the path afterwards through some specific pref pane without being enclosed at $HOME, your solution might do it well.	[reply]
Re: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? by GrandFather (Saint) on Mar 16, 2012 at 05:32 UTC
I that situation I use place holder text that is replaced at run time using a regex and a hash lookup. Something like the following: `my %subs = (home => 'HomePathFromConfigOrEnv'); my $keyMatch = join '\|', keys %subs; my $cfgStr = '!home!/path'; $cfgStr =~ s/!($keyMatch)!/$subs{$1}/g; print $cfgStr;` [download] Prints: `HomePathFromConfigOrEnv/path` [download] True laziness is hard work	[reply] [d/l] [select]
Re: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? by LanX (Saint) on Mar 15, 2012 at 20:00 UTC
You can use eval, but be aware about the risk of injections if others edit your config. Cheers Rolf	[reply]
Re^2: What's the best way to convert a non interpolated single-quoted string into an interpolated double-quoted string? by emilbarton (Scribe) on Mar 15, 2012 at 20:12 UTC
Yes it's clearly the basic trick, except that I couldn't use eval in this particular case.	[reply]