sub myTrim {
    my $str = shift;  #shift faster than @_ for one paramater
    $str =~ s/^\s*//; #no space at front
    $str =~ s/\s*$//; #no space at rear
    return $str;
}
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Trimming leading and trailing whitespace from a string is a FAQ. Like you, I think it's simplest and clearest to do it in two simple statements. To nickpick your solution, it's better to replace * with + like so:

    $str =~ s/^\s+//;    # no whitespace at front
    $str =~ s/\s+$//;    # no whitespace at rear
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See also:

• trim leading & trailing whitespace (Perl Monks)
• Perl Cookbook
• Perl Maven
• Re: Is there a way to make these two regex lines cleaner? (new builtin trim function for perl 5.34.1)
• Code review: function to trim whitespace from all items in a list