@x = qw/Foo Bar Blaz/;
#@x = qw//;

print "Before: @x$/";
while ( my $ele = <@x> ) {
 next unless $ele;
 print "$ele becomes ";
 $ele =~ s/^(.)/x$1/;
 print $ele . $/;
}
print "$/After: @x";
__END__

Then I have :
  Before: Foo Bar Blaz
  Foo becomes xFoo
  Bar becomes xBar
  Blaz becomes xBlaz

  After: Foo Bar Blaz