An alternative to using join and string concatenation when making the pattern would be to change the default list separator from a space to the pipe symbol and use interpolation with the array or list.

$ perl -Mstrict -Mwarnings -le '
> my @arr = qw{abc d.ef gh?i};
> my $patt;
> {
>     local $" = q{|};
>     $patt = qq{xyz(@{ [ map quotemeta, @arr ] })123};
> }
> print $patt;'
xyz(abc|d\.ef|gh\?i)123
$
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You can also use this method with qr{...} which behaves like double quotes.

Cheers,

JohnGG