Select Code to Download

left          \1=left \2=
right         \1=     \2=right
rightabc      \1=     \2=rightabc
leftright     \1=left \2=right
leftrightabc  \1=left \2=rightabc

s/(.*)(right)?/\1 <> \2/

echo "left"|perl -ne 'print if s/(.*)(right)?/\1 <> \2/'              
+  left <>
echo "right"|perl -ne 'print if s/(.*)(right)?/\1 <> \2/'             
+  right <>
echo "leftright"|perl -ne 'print if s/(.*)(right)?/\1 <> \2/'         
+  leftright <>

s/(.*(?=right.*)|(.*))/\

echo "left"|perl -ne 'print if s/(.*(?=right.*)|(.*))/\1 <> \2/'      
+  left <> left
echo "right"|perl -ne 'print if s/(.*(?=right.*)|(.*))/\1 <> \2/'     
+  <> right
echo "leftright"|perl -ne 'print if s/(.*(?=right.*)|(.*))/\1 <> \2/' 
+  left <> right