$ perl -mO=Deparse -e 'if ( $1 eq 'A' || $1 eq 'B' ) { }'

if ($1 eq 'A' or $1 eq 'B') {
    ();
}
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:) I'm a bit surprized to see that things seem to be OK despite the lack of apostroph escaping - but you see that, at least in this case, 'or' is quite OK.
Anyway, I try to follow the advice in Damian Conway's "Perl Best Practices" and prefer to write that as

if( ($1 eq 'A') or ($1 eq 'B') ) { ...}
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