Looking for alternative syntax for assigning variables based on regex matches

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

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Re: Looking for alternative syntax for assigning variables based on regex matches by haukex (Archbishop) on Mar 02, 2021 at 05:24 UTC
`my ($x,$y) = $foo =~ /(hello)(world)/ or die "failed to match"; if ( my ($x,$y) = $foo =~ /(hello)(world)/ ) { print $x, $y; } if ( $foo =~ /(?<x>hello)(?<y>world)/ ) { print $+{x}, $+{y}; }` [download] Update: The first two work like any other variable assignment, so `($foo) = $foo=~/(hello)/;` works too of course. (Update 2: If assigning back to the same one variable, so does `s///` and its variations.)	[reply] [d/l] [select]
Re: Looking for alternative syntax for assigning variables based on regex matches by rsFalse (Chaplain) on Mar 02, 2021 at 10:28 UTC
With non-destructive /r modifier (and lookahead): `perl -wle '$foo = "a hello w"; $foo = $foo =~ s/(?=.(hello))./$1/sr; + print $foo'` [download] OUTPUT: `hello` [download] And if you want only to use your capture, just: `...; print $foo =~ s/(?=.(hello))./$1/sr;` [download] In the later example a value of `$foo` didn't change. *Updated +one more way: `...; $foo =~ /hello(?{ $foo = $& })/; print $foo` [download] Though it looks like bad practice to change a variable while it is in use.	[reply] [d/l] [select]
Re: Looking for alternative syntax for assigning variables based on regex matches by Marshall (Canon) on Mar 02, 2021 at 22:14 UTC
An idea for you: `use strict; use warnings; my $foo ="some hello message"; my ($hello) = $foo =~ /(hello)/; $hello //= ''; # null string if "hello" was not found __END__ $hello will be either "hello" or a null string. Better than an undef value. Amongst other things, this maintains a "printable value" for $hello. use $hello in a Boolean context. $foo is a string. Do not reuse that string variable name to mean something different. Create new Boolean variable.` [download]	[reply] [d/l]
Re: Looking for alternative syntax for assigning variables based on regex matches by Anonymous Monk on Mar 02, 2021 at 13:58 UTC
"There's More Than One Way To Do It." – Tim Toady. However you choose to do it, make your code easy for a human reader to understand, and easy to change in one small, targeted, "git" commit. What you've written is clear enough, and I would just keep doing it.	[reply]