Re^3: Another Pattern Matching Question

in reply to Re^2: Another Pattern Matching Question
in thread Another Pattern Matching Question

Your solution which adds R? to the original regex was on the right track and achieves what you want, albeit poorly:

$ perl -Mstrict -Mwarnings -E 'my $fileName;
my $re = qr{3B4[0|1|2]RT\.\d{10}\.\d+R?\.bin};
$fileName = "3B40RT.2000033121.7.bin.gz";
say +($fileName =~ /$re/) ? "match" : "no match";
$fileName = "3B40RT.2000033121.7R.bin.gz";
say +($fileName =~ /$re/) ? "match" : "no match";
'
match
match
[download]

I don't think you understand character classes or alternation (perhaps both). Where you're trying to match a 0, 1 or 2 in the same position, [0-2] would be far better than [0|1|2] (which is trying to match a 0, pipe, 1, pipe or 2 in the same position) - the 2nd pipe is redundant and the 1st pipe isn't wanted anyway. So, here's an improved version:

$ perl -Mstrict -Mwarnings -E 'my $fileName;
my $re = qr{3B4[0-2]RT\.\d{10}\.\d+R?\.bin};
$fileName = "3B40RT.2000033121.7.bin.gz";
say +($fileName =~ /$re/) ? "match" : "no match";
$fileName = "3B40RT.2000033121.7R.bin.gz";
say +($fileName =~ /$re/) ? "match" : "no match";
'
match
match
[download]