perl -le '$t="a/b"; if ($t =~/^(.*?)\//){$z=$1}elsif($t=~/\/(.*)/){$z= $1} print $z'
#prints a

perl -le '$t="/b"; if ($t =~/^(.*?)\//){$z=$1}elsif($t=~/\/(.*)/){$z= $1} print $z'
#prints nothing