> BEFORE AND AFTER THE MATCHED SEQUENCE HOW I CAN DO IT?????

Hmm ... most probably you have a hard ware problem.

Your caps lock and your question mark keys seem broken.

And your post button seems to go wild in opening new threads: Reaped: STRING QUESTION

HTH!

#!/usr/bin/perl -l

my $seq  = "atgtagat";
my $find = "gta";

my ($before, $after) = $seq =~ /(..)$find(..)/;

print "before: $before";    # "at"
print "after:  $after";     # "ga"
[download]

my ($before, $after) = $seq =~ /(..)$find(..)/;
[download]

... will find only one instance of a sub-sequence in a sequence. The following will find multiple instances of sub-sequences, either overlapping or non-overlapping:

>perl -wMstrict -le
"my $seq  = 'atggggtaggggat';
 my $find = 'ggg';
 print 'non-overlapping:';
 while ($seq =~ m{ (..) $find (..) }xmsg) {
   print qq{($1)$find($2)};
   }
 print 'overlapping:';
 while ($seq =~ m{ (?= (..) $find (..)) }xmsg) {
   print qq{($1)$find($2)};
   }
"
non-overlapping:
(at)ggg(gt)
(ag)ggg(at)
overlapping:
(at)ggg(gt)
(tg)ggg(ta)
(ta)ggg(ga)
(ag)ggg(at)
[download]