shell> perl -le 'print "yep" if "foo bar" !~ /baz/'
yep

##</code><code>##

shell> perl -le '$_="xfoo"; print; substr($_,0,1)=""; print'
xfoo
foo

##</code><code>##

shell> perl -le '$_="xfoo"; print; s/^.//; print'
xfoo
foo

##</code><code>##

shell> perl -le '$_="foo,bar,baz"; print; s/,[^,]+$//; print'
foo,bar,baz
foo,bar