.abc(abc),

##</code><code>##

chop($line);              # Best way. Removes the last character.
$line =~ s/.\z//s;        # Works, but not as simple as 'chop': substitution.
substr($line, -1,1,'');   # Works, but not as simple as 'chop': substr with empty-string replacement.
substr($line,-1,1) = '';  # Works, but not as simple as 'chop': substr as an lvalue.

##</code><code>##

.abc(abc),\n

##</code><code>##

$line =~ s/.$//;

##</code><code>##

chomp $line;
chop $line;

##</code><code>##

$line =~ s/.\n?$//;