Re^5: search of a string in another string with 1 wildcard

in fact, your code shouldn't be some thing like
my $pattern = qr{ab[crdnfqm]def};
if $string =~ m{ ($pattern) };
....
which doesn't find all strings with the pattern.

That is perhaps because the regex m{ ($pattern) } (which lacks the /x regex modifier) requires a space before and after $pattern in order to match.

I don't understand trailing xms at the end of pattern.

These are regex modifiers. The /x modifier makes the regex compiler ignore whitepace (for improved readability). The /m and /s modifiers control the behavior of, respectively, the ^ $ (string end) and . (dot) metacharacter operators. I have adopted the best practice recommended by TheDamian of always (well, almost always) including these modifiers in every qr// m// s/// regex I write. The reason for this is to improve regex readability (/x) and to make explicit the behavior of the ^ $ . operators (/ms).

Please see perlre, perlrequick, and perlretut.

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Re^6: search of a string in another string with 1 wildcard by carolw (Sexton) on Oct 15, 2014 at 11:17 UTC
How to add + and space to the construct? So instead of `my $pattern = qr{ab[crdnfqm]def}; my $pattern = qr{ab[crdnfqm\+\s]def};` [download] will be correct? to be used with your solution `if $string =~ m{ ($pattern) };` [download]	[reply] [d/l] [select]
Re^7: search of a string in another string with 1 wildcard by AnomalousMonk (Archbishop) on Oct 15, 2014 at 14:58 UTC
The regex definition `qr{ab[crdnfqm\+\s]def};` does add a `'+'` character and the class of all whitespace characters to the `[crdnfqm]` character class contained in the previous `qr{ab[crdnfqm]def};` definition. Note, however, that `m{ ($pattern) }` (still) requires a blank (0x20) character before and after `$pattern` in order to have a match. (NB: The `'+'` character is not special, i.e., is not a metacharacter, inside a character class and so does not need the `\` escape — but it does no harm.) Please see perlre, perlrecharclass, perlrequick, and perlretut.	[reply] [d/l] [select]