This is an issue with DBI placeholders and not strict. Your problem is that you're calling execute() with a placholder value where your SQL doesn't have a placeholder in it. Your code should probably look more like this (formatting added for my own benefit :)

my $sqlcount = 'SELECT COUNT(*) FROM grp_def WHERE grp_name = ?';

my $sth = $dbh->prepare($sqlcount)
  or die "Cannot prepare: " . $dbh->errstr();
$sth->execute($grp_name)
  or die "Cannot execute: " . $sth->errstr();

my $occurences = $sth->fetchrow_arrayref->[0];

print "result: $occurences\n";
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There I've moved $grp_name out of the SQL and moved into the execute() and replaced it with a placeholder. For more info on placeholders see the Placeholders and Bind Values section of the DBI docs.
HTH

_________
broquaint