if( grep(/$var1/, @arr1) )
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or

if( grep {/$var1/} @arr1 )
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or

if( grep { $_ eq $var1} @arr1 )
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Your usage of grep evaluates $var1 for every instance of @arr1, then happily returns the element for which the evaluation of $var1 succeeded. See grep.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}