The pipe character is not whitespace. You can mention it in the regex, you even do not have to backslash it, because it appears in a character class: 
while (<>) {
    if (/^(>[^|]*)/) {
        print "$1\n";
    } else {
        print;
    }
}

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لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: trim header lines in files by choroba
in thread trim header lines in files by utpalmtbi

Title:
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