$s ='25 {fred and barney} text 2.36 12.0 {bam bam} text {pebbles}';
$n=0;    $s =~ s'{.*?}'{$sub[$n++]}'g;
print $s;

25 {$sub[$n++]} text 2.36 12.0 {$sub[$n++]} text {$sub[$n++]}