in reply to How to add perl variable before any text in perl code

Use ${artpage} (see Scalar values): 
$boxtxt=~s/<\/boxed-text>/<p><inline-supplementary-material mimetype=\
+"video\" mime-subtype=\"avi\" xlink:href=\"${artpage}video_clip_$vide
+oid\.avi\">Download Video $videoid<\/inline-supplementary-material><\
+/p><\/supplementary-material>/g;

[download]

In Section Seekers of Perl Wisdom