Match a Variable to Only the True Statement

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

Thanks to the forum here I am now aware of how to create and assign variables within an if statement to matched variables. Now I'm trying to set the same variable $m1 with the below statements. Only one pattern will evaluate true at a time, so how do I assign $m1 to only the one that evaluates true without evaluating the other (that seems to clear $m1 if the last pattern evaluated is false)? Thank you as always, the script is coming along perfectly!

Update: In my effort to simplify, I did change one thing, which I believe makes things a bit more difficult; the 3rd matching statement is with a different string(output_2) to pattern match, so I rewrote it correctly below. That said, I believe what will make this work is to somehow only evaluate statements until one is shown to be true, then to breakout with $m1 set

if(my ($m1) = $output =~ /^(pattern1)$/ or my ($m1) = $output =~ /^(pa
+ttern2)$/ or my ($m1) = $output_2 =~ /(pattern3)/) {
$hash{$key} = $m1;
}
[download]

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Re: Match a Variable to Only the True Statement by AnomalousMonk (Archbishop) on Jan 31, 2016 at 20:31 UTC
It's not clear to me exactly what you're trying to do, but I wonder if perhaps you need an `\|` "ordered alternation" operator: `c:\@Work\Perl\monks>perl -wMstrict -le "my $p1 = qr{ Foo }xms; my $p2 = qr{ Bar }xms; my $p3 = qr{ Zot }xms; ;; my $str = 'Bar'; ;; if (my ($m) = $str =~ m{ \A ($p1 \| $p2 \| $p3) \z }xms) { print qq{matches: has '$m'}; } " matches: has 'Bar'` [download] Update: `my ($m1) = $output =~ /^(pattern1)$/ or my ($m1) = $output =~ /^(pattern2)$/ or my ($m1) = $output =~ /(pattern3)/` BTW: An expression like the one quoted above, with multiple masking variables (i.e., variables having the same name) defined in the same scope is never a good idea, and Perl would have told you about this ugly situation had you enabled warnings with a `use warnings;` statement at the top of your program. Especially for those just starting with Perl, always `use warnings;` and `use strict;` at the start of your code. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: Match a Variable to Only the True Statement by poj (Abbot) on Jan 31, 2016 at 21:12 UTC
`if ( $output =~ /^(pattern1\|pattern2)$/ ){ $hash{$key} = $1; } elsif ( $output_2 =~ /(pattern3)/ ){ $hash{$key} = $1; }` [download] poj	[reply] [d/l]