P:\test>perl -le"$_='old value';@a=1..10; for(@a){ $_++ }; print;"
old value

##</code><code>##

P:\test>type junk.dat|perl -e"$_='old value';{local$_; while(<>){print};}print;"
line 1
line 2
line 3;
old value

##</code><code>##

P:\test>type junk.dat|perl -e"$_='old value';while(<>){ print};print;"
line 1
line 2
line 3;