all the files that begin with messages and MAY have a "." and a digit behind it, but it should not match something that has say .txt, .pl, etc.

Having a directory populated with these files

messages
messages.
messages.1
messages1.2.3
messages.1.gz
messages.2
messages.3
messages.pl
messages.txt

[download]

the following code 

opendir D, '.';
while(readdir D) {
   /^messages(?:\.\d?)?$/ and print $_,"\n";
}

[download]

will output those:

messages.
messages.2
messages
messages.1
messages.3

[download]

The elements of that regular expression can be best explained using the x modifier (see perlre and perlfunc): 

opendir D, '.';
while(readdir D) {
   m/            # begin of match
       ^         # match at the beginning of element, i.e. $_
       messages  # match 'messages' literally
       (         # begin of match group
        ?:       # subject to * ? +  not creating a capture
          \.     # match a period
          \d?    # optionally (?) match a digit
       )         # end of match group
       ?         # which may or not occur
       $         # before the end of the string
    /x           # tell m// that we use extended regex w/comments
    and          # if found
    print "$_\n" # print it out.
}

[download]
perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In reply to Re: Regex for files by shmem
in thread Regex for files by bmcquill

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