G'day perl-diddler,

Firstly, I suggest you read "perlop: Regexp Quote-Like Operators". There are certain things about qr that are non-standard and non-intuitive: I suspect you're making understandable, yet incorrect, assumptions.

In the following, I've addressed all (I think) of the points you've raised and hopefully cleared up any misunderstandings.

When used as a string, qr acts like a string: 

$ perl -E 'my $re = qr{([0-6BS])}; say $re'
(?^u:([0-6BS]))

[download]

When used as a reference, qr acts like a reference: 

$ perl -E 'my $re = qr{([0-6BS])}; say ref($re)'
Regexp

[download]

When used as a hash key, which is a string, qr acts like a string: 

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; 
+say $y[0]'
(?^u:([0-6BS]))

[download]

The hash key is just a string, not a reference: 

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; 
+say "|", ref($y[0]), "|"'
||

[download]

The next two points directly address the title of your post: "how to use string RE (against $_ and capture)".

You can use qr in a match like '/COMPILED_QR_RE/': 

$ perl -E 'my $re = qr{([0-6BS])}; $_ = "B"; /$re/; say $1'
B

[download]

You can use a hash key string in a match like '/STRING_RE/': 

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; 
+$_ = "B"; /$y[0]/; say $1'
B

[download]

See also: perlre and ref.

— Ken

In reply to Re: how to use string RE (against $_ and capture) by kcott
in thread how to use string RE (against $_ and capture) by perl-diddler

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