#!/usr/local/bin/perl

# The BstYI restriction enzyme cuts at the consensus sequence rGATCy, 
# namely A or G in the first position, then GATC, and then T or C.

# To find out whether a sequence contains a restriction site for BstYI, write
  
  if ($sequence =~ /[AG]GATC[TC]/) {
  # do something here
  };

  # This will match all of AGATCT, GGATCT, AGATCC, GGATCC.