$tu ="D:\\PERL\\crc_test\\shock_api.h";
print "match:$&\n" if $res=$tu=~ m/\.c$/ ;
print "match:$&\n" if $mes=$tu=~ m/\.h$/ ;
if ($mes=$tu=~ m/\.h$/ or $res=$tu=~ m/\.c$/)
{
    open FH, $tu or die "cannot open the required file :$!\n";
    while ( my $line = <FH>)
    {
        $line =~ s/\\t/    /g;
    }
close (FH) or die "cannnot close the required file:$!\n";
}
else
{
    print "out of loop\n";
}