It looks like you are trying to extract a part of a string that comes before the period.

use strict;
use warnings;

print StrBefore('abc.com', '.');

#
# This function splits a string into two parts
# at the first occurence of SUBSTR.
# Returns the first half of the string.
#
#  Usage: STRING = StrBefore(STRING, SUBSTR)
#
#  Example: StrBefore("Abcdef", "cd") --> "Ab"
#           StrBefore("abc.us", ".")  --> "abc"
#           StrBefore("tree", ".")    --> "tree"
#
sub StrBefore
{
  @_ or return '';
  my $S = shift;
  defined $S or return '';
  length($S) or return '';
  @_ or return $S;
  my $B = shift;
  defined $B or return $S;
  length($B) or return $S;
  my $P = index($S, $B);
  return ($P < 0) ? $S : substr($S, 0, $P);
}
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