sub modify {
chomp( $_[0] );
# whatever else happens, you've just potentially modified $_[0]
}
modify('fred');
# What would you expect to happen to 'fred'?
####
Modification of a read-only value attempted at /tmp/t.pl line 2.
####
Can't modify constant item in modify at -e line 1, at end of line
Execution of -e aborted due to compilation errors.