Thank you all for your answers. Meanwhile I found answer myself to my question.

@a2 = map chr hex, @a1;
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can be written as

@a2 = map chr(hex()), @a1;
# or
@a2 = map chr(hex($_)), @a1;
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And the original syntax can be used in a simple assignment statement like this.

$x = char hex 41; # which means $x = 'A';
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