>perl -le"my $s = chr(0xE1); print $s =~ /\p{Alpha}/ ?1:0"
1

>perl -le"my $s = chr(0xE1); print $s =~ /[\p{Alpha}]/ ?1:0"
1

>perl -le"my $s = chr(0xE1); utf8::upgrade($s); print $s =~ /[[:alpha:]]/ ?1:0"
1