perl -i.old -lne 'if (/^[\s#]*Port/i) { print "Port 1234" unless $done++ } else { print }' sshd_config

##</code><code>##

perl -i.old -lne 'print unless /^[\s#]*Port/i; END{print "Port 1234"}' sshd_config

##</code><code>##

PORT=1234 perl -i.old -lne 'print unless /^[\s#]*Port/i; END { print "Port $ENV{PORT}" }' sshd_config

##</code><code>##

perl -i.old -lne 'BEGIN { $sshport = pop }; print unless /^[\s#]*Port/i; END { print "Port $sshport" }' sshd_config 1234