You have a control-M character after your '-w':

$ cat -v xx
#!/usr/bin/perl -w^M

print "test\n";
$ /opt/perl/5.005_02/bin/perl xx
 on #! line at xx line 1.
$ /opt/perl/5.6.0/bin/perl xx
test
[download]

So, either upgrade, or remove the ^M character.

Abigail