Doing such things with regex is no fun, and easily done wrong. Using Mojo::DOM:

#!/usr/bin/perl

use strict;
use warnings;
use Mojo::DOM;
use feature 'say';
my $html = '<span class="Trsdu(0.3s) Fw(b) Fz(36px) Mb(-4px) D(ib)" da
+ta-reactid="33">';

my $dom = Mojo::DOM->new( $html );

say $dom->at('span.[class^=Trsdu]')->attr->{'data-reactid'};
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Output:

33
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