The elements of @_ are all aliases to the original arguments, so if they are lvalues they can be modified.

sub strip_space {
    s/\s//g for @_;
    1;
}

my $test = "this will have no spaces!";
strip_space($test);
print $test,$/;

__END__
thiswillhavenospaces!
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That will not work for constant arguments,

# strip_space("this will have no spaces!");
# modification of constant error
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