$str = "234kjh23ljkgh34klj2345klj";
$str =~s/(?<=[a
-z
])(?=[0-9])|(?<=[0-9])(?=[a
-z
])/ /ig
;
JHN0ciA9ICIyMzRramgyM2xqa2doMzRrbGoyMzQ1a2xqIjsKcHJpbnQgJHN0ci4iXG4iOwokc3RyID1+cy8oPzw9W2Etel0pKD89WzAtOV0pfCg/PD1bMC05XSkoPz1bYS16XSkvIC9pZzsKcHJpbnQgJHN0ci4iXG4iOw==